1. Field of the Invention
The present invention relates to devices, systems, and processes useful for signal conditioning.
2. Brief Description of the Related Art
Control systems automate our world. From assembly lines to home heating and cooling systems, sensors detect various conditions, and report those conditions with discrete signals to a controller. The controller is programmed to keep the system running by feeding back commands determined by the various signals it receives. The processor feeds command signals back to controllers to operate equipment that perform work. Input/Output (I/O) devices feed information between sensors and controllers. To send discrete signals back and forth through the system, signal conditioning must be performed.
One problem found in control system design is integrating different discrete signal formats. Many different types of sensors may be used in a system. For example, a mail processing system may have optical character recognition scanners, and scales, along with other types of sensors, to sort mail. These sensors are manufactured by different companies, and have different discrete signal formats. Thus, the problem of integrating discrete signal formats is continuously present in control systems.
Another problem in designing control systems is encountered when bridging the gap between existing, or legacy, technology, and current computer architecture. Particularly, control systems have moved towards a distributed architecture, where a single controller controls signal discretes (“discretes”) that are distributed along a common FieldBUS (Device-Level Network). Legacy systems typically have several central processing units (CPUs) controlling various subsystems and accessing discrete signals locally, with a custom format, rather than a common architecture. Increased performance of CPU's has enabled and driven the migration towards distributed I/O systems. If the legacy system cannot be interfaced with a distributed system, the user is faced with purchasing and testing a completely new automation system. This complete replacement is often too costly and time consuming to be feasible.
Discrete signals must be conditioned when interfacing the legacy and distributed systems. If the signals are compatible, the discrete may be left alone. Otherwise, the discrete may need to be interrupted, redirected, or over-ridden. In current systems, conditioning legacy discretes has typically been approached in two ways. One approach has been to place a communications link between the legacy controller and the distributed system controller, and allow this new controller to make requests from the legacy system. This approach, however, does not give the distributed system real-time control. Another approach to conditioning legacy discretes has been to alter the existing hardware, effectively generating a new discrete signal format. This approach, however, again requires custom alteration to the existing system, requiring testing and equipment replacement.
Various devices, systems and methods are known for conditioning signals in control systems. U.S. Pat. No. 6,392,557 to Kreuter, issued May 21, 2002, describes an output over-ride board 10 releasably mounted to a programmable logic controller 12 (PLC) that controls an output of the PLC 12. The over-ride board is particularly used for over-riding the output signal from a PLC so that the PLC can be modified at the installation sight (col. 4, 11. 23-28.)
U.S. Pat. No. 5,947,748 to Licht, et al., issued Sep. 7, 1999, for a connector to a PLC. The interface connector board 16 evenly distributes thermocouple wires providing input to the PLC. A plurality of dielectrically isolated interconnection points permits the user to custom design components used for signal conditioning (col. 3, 11. 5-30).
Although prior systems, methods, and devices generally functioned well and provided advantages over prior systems, methods, and devices, they do not provide a simple, efficient, and cost-effective manner of conditioning legacy discrete signals interfaced with a distributed system architecture.